Artificial reefs are commonly found around the world. Some are constructed to protect harbors or beaches from wind, wave or tidal forces. These types of reefs are often constructed of large, boulder-sized stones or concrete modules cast in a variety of shapes and sizes.
Reefs designed for protection purposes generally extend above the water line so as to deflect the forces of wind, wave or tide. These protective artificial reefs can be of any size or shape; sometimes they are circular, semi-circular, curved or straight. When a reef is constructed to abut a shoreline, it is sometimes called a break wall. When a reef extends from the shoreline into open water, it is sometimes called a jetty. Whatever they are called, they are, in essence, an artificial reef.
Artificial reefs are often favored by fishermen, because their structure, whether constructed of natural stone or concrete modules, creates prime shelter and habitat for a wide variety of marine organisms, including desirable species such as fish, crab and lobster that are prized by both commercial fishermen and recreational sports fishermen.
Other artificial reefs are constructed solely to enhance marine habitat and are designed to provide an underwater landscape replete with nooks, crannies, cavities, ledges and other subsurface features onto and into which marine organisms may attach or shelter. By providing cover and sanctuary for small organisms like algae, plankton and minnows, larger fish are attracted to forage. These fish, in turn, attract even larger fish, including sharks, tuna, bass, snapper, grouper and other large predatory fish which are at the top of the marine food chain. These types of reefs are usually totally submerged and may be constructed in shallow water near shore or in deep water miles off shore.
These types of reefs may be constructed of almost any material or objects which will sink into the water column, including, but not limited to the following: natural stone, weighted tree stumps and brush, household appliances, cars, trucks, farm implements, school buses, scrap steel, subway and railway cars, factory machinery and other. Additionally, any number of decommissioned naval and merchant ships of all sizes have been scuttled in deep water to provide artificial reef structure. These types of reefs may also be constructed of cast concrete modules that can take a variety of shapes and which may have cavities molded into them.
Increasingly, artificial reefs are becoming a part of the underwater landscape wherever there is a robust interest in fishing, either for commercial or recreational purposes, or both. As an example, many U. S. states with salt water territories actively construct artificial reefs for use by recreational sports fishermen. The reef locations appear on nautical charts, and buoys are positioned over them so they may be easily located by mariners and fishermen. Certain countries, notably Japan, construct artificial reefs on a large scale for use by their commercial fishing fleets. Wherever artificial reefs are constructed, they are widely considered to be an enhancement to the marine environment and ecosystem.